My invention is directed to a combustion apparatus and, more particularly, to a combustion apparatus used to heat furnaces and the like by burning gas or oil in a manner that results in a reduced amount of oxides of nitrogen in the products of combustion.
Industry's increased awareness of the harmful effects of oxides of nitrogen (hereinafter "NOx") and the stringent requirements set by government environmental agencies regarding the amount of this pollutant that can be emitted by a furnace into the atmosphere have created a demand for furnace combustion devices that burn fuel so that the exhaust gases contain low amounts of NOx. To achieve this reduction, it is desirable to burn a rich fuel mixture in a low temperature flame while recycling the unburned mixture.
As will be described below in greater detail, my combustion method claimed in U.S. Pat. Nos. 3,876,362 and 3,954,382 utilizes a rich fuel mixture and a low temperature flame to reduce the levels of NOx in the products of combustion. The method claimed in these patents comprises injecting fuel at a high velocity through a cylindrical burner tile structure to a combustion chamber and deflecting the stream against the inside wall of the structure, thereby causing a counterflow of high temperature combustion gases from the combustion chamber back through the tile structure to mix with the injected fuel. Air in a quantity less than theoretical air is supplied through an annular passage to the mixture as it enters the combustion chamber thereby promoting endothermic gasification of the fuel before it enters the combustion chamber which results in the fuel rapidly and completely burning at a relatively low temperature.
In order to promote the mixing of the combustion air with the fuel mixture, vanes are placed in the passage supplying the combustion air to the combustion chamber so that the air enters the combustion chamber in a spinning stream. However, the apparatus of these patents has the disadvantage of causing a rapid burning of the fuel mixture which restricts flame size and tends to give it a somewhat uneven temperature.